2012 April 19, Josh Halliday, “Free speech haven or lawless cesspool – can the internet be civilised?”, in the Guardian‎[1]:

But the purported rise in violent videos online has led some MPs to campaign for courts to have more power to remove or block material on YouTube. The Labour MP Heidi Alexander said she was appalled after a constituent was robbed at knifepoint, and the attackers could be found brandishing weapons and rapping about gang violence online.

Thus, the postulation of a Noun Phraseconstituent is justified on morphological grounds, since it is not obvious how we could describe the grammar of the genitive 's inflection in English without saying that it's a Noun Phrase inflection.